1. Field of the Invention
The present invention relates to an air bypass device, in which bypass air bypasses a throttle valve and is supplied to an intake passage at the down stream side from the throttle valve. More particularly, the present invention relates to an air by pass device in a multiple throttle body, in which a single air bypass device is used, and bypass air is supplied to intake passages at the down stream side from throttle valves of respective throttle bodies constituting the multiple throttle body.
2. Description of the Conventional Art
Japanese Patent Application Laid Open No. 2002-89415 discloses a conventional air bypass device.
The conventional air bypass device will be described using FIG. 6(b) in the relevant patent gazette (names and codes used in the gazette are used). An inlet 31 of a bypass passage is opened in a bottom part of a cylindrical valve body housing chamber 32. A circular first upstream side branch passage 36 and a circular second upstream side branch passage 37 are opened on an inner peripheral wall of the valve body housing chamber 32.
Openings of the first and second upstream side branch passages 36 and 37 opened on the inner peripheral wall of the valve body housing chamber 32 are controlled by a bypass valve 33 operated by a valve body drive mechanism 34.
Further, the first upstream side branch passage 36 is connected with a first downstream side branch passage 63, and the downstream of the first downstream side branch passage 63 is connected with an intake passage at the downstream side from a first throttle valve.
Further, the second upstream side branch passage 37 is connected with a second downstream side branch passage 65, and the downstream of the second downstream side branch passage 65 is connected with an intake passage at the downstream side from a second throttle valve.
Accordingly, openings of the first and second upstream side branch passages 36 and 37 opened in the valve body housing chamber 32 are controlled by a stroke of a bypass valve 33. Bypass air corresponding to the openings is supplied to the intake passages at the downstream side from the respective throttle valves through the first and second downstream side branch passages 63 and 65. Thus, an idling operation of an engine corresponding to atmosphere temperature of an engine can be carried out.